This invention relates to a cathode ray tube comprising electrostatic deflection means positioned along the path of an electron beam e.sub.f generated by an electron source.
In a cathode ray tube it is usual to deflect the path of the electron beam by means of an electrostatic deflection produced by plates set up at different potentials. The cathode ray tube usually comprises a pair of plates for the horizontal deflection on which a time base is applied and a pair of plates for the vertical deflection on which the electric signal to be analyzed is applied. Said electric signal is introduced into the tube by means of connectors and cables which are connected to a signal generator. Said signals may be generated at first in forms which are non-electric. A conversion into an electric signal is thus necessary, which may be inconvenient or difficult in certain situations.
Said signals may have various frequencies. For rapid or high frequency signals it may be desired to realise, for example, an oscilloscope having a passband which covers several hundreds of MHz. This is, however, difficult to realise with such electrostatic deflection means. Solutions have been suggested using wave propagation techniques.
The document entitled "Les tubes a rayons cathodique a propagation d'ondes a tres large bande" by C. Loty, Acte Electronica vol. 10, no. 4, 1966, pp. 351-361, reveals a solution using a wave line in the form of a helix. In this case a wave line of constant division is constituted by a coiled wire conductor along which the wave propagates at the speed of light according to a three-dimensional structure. An oscilloscope based on such a structure has a very high passband. However, the signals which are to be analysed and which act on the electrostatic deflection of the electron beam are to be introduced in an electric form by means of connection cables which have non-negligible capacitances. In practice, there is always the problem of sensitivity and the designer is required to establish a compromise between the speed and the sensitivity of the deflection of the electron beam.
So when light phenomena are analysed which may be of an extremely short duration, a considerable part of the rapid information which they comprise may be concealed and may even be lost by said introduction difficulties of the electric signals in the cathode ray tube, which makes the inconveniences even worse.
So, the solution to the problem posed is to avoid the conversion of optical signals. Moreover, it also may be desired to preserve in the tube a great sensitivity and a high speed for the analysis of such rapid light signals.